Windows and doors typically are installed in rough openings of buildings and secured with fasteners, which sometimes are driven through peripheral nailing fins into the underlying framing. It is common to apply flashing strips around the exterior brick mould of the window or door frame to prevent water leakage. Flashing applied across the top or head mould of the door or window frame is sometimes referred to as head flashing or drip flashing. Drip flashing generally is L-shaped in cross-section and is installed atop the top brick mould with one leg overlying the upper edge of the brick mould and the other leg overlying, and often nailed and taped to, the adjacent wall surface. A continuous dam is thus formed where the top brick mould meets the wall to intercept and prevent the migration of water. It is common for drip flashing to be formed with a downturned lip referred to as a drip edge that slightly overlies the face of the head mould around its upper edge. The same flashing may be applied along the sides of the window or door to form a water barrier, although in these applications the drip edge generally is superfluous.
Applying flashing around square or rectangular windows and doors is straight forward. Elongated L-shaped flashing strips, which may be formed of sheet metal or plastic, are cut to length, nailed in place around the brick mould, and may be taped with flashing tape to prevent drafts. Increasingly, however, windows and doors are used that have an arched rather than a straight top. Applying flashing around an arched top presents a unique problem because traditional L-shaped flashing will not bend or arch around the curved brick mould without deforming. Notching the leg that lies against the wall to allow the structure to bend has been suggested, but such notches can breach the continuous dam otherwise formed and can degrade the reliability of the flashing. Special drip flashing made of flexible material and held in place with rigid brackets also has been suggested as has drip flashing with one corrugated or accordion-folded leg, but these also have not been satisfactory. As a consequence, many builders and installers order specially molded or formed curved drip flashing to fit the particular doors and windows being installed, which is expensive and troublesome.
A need therefore exists for a window and door flashing that can be installed easily around square or rectangular doors and windows and, just as easily and without special modification, around arch-topped windows and doors to form drip flashing. Such a flashing should retain a continuous uninterrupted dam where the arched brick mould meets the wall and should be easily installable without special brackets or other ancillary items. It also should be rollable for packaging and shipping so that it can be supplied in long bulk lengths.